Long-range attraction in the collisions of free-molecular and transition-regions aerosol particles
An aerosol is the transitional condition of matter between the equilibrium gas and condensed states. This paper reviews recent advances in the description of the compositional dependences of free molecular and transition regime aerosol collision rates that are essential to the understanding of the evolution of this nonequilibrium condition of matter. To set the physical context, selected current advances in homogeneous nucleation theory are described. These results, which are based upon metastable equilibrium prior to the onset of nucleation, are related to the nonequilibrium collisions of post-critical nuclei or aerosols. Since all particles interact via attractive potentials whose mathematical forms become singular at contact, a new procedure is described which has been developed for computing the free molecular collision rates of spherical particles that both exploits this singularity and is readily generalizable to transition regime collisions. The physics of the molecular van der Waals interaction and its mathematical form for interacting point dipoles with arbitrary retardation are reviewed. Difficulties in the straightforward generalization of the molecular theory to condensed media interactions are pointed out and used to motivate the Lifshitz theory of the van der Waals interactions of condensed media. A model for the spectral retardation of the sphere-sphere interaction potential is introduced and used in computations of those energies for 1 to 100 nm radii spheres of several materials. These energies are used in the computation of collision rate enhancements over the hard-sphere collision rates, the properties of these enhancements including the effects of retardation are discussed, and they are compared with experiment where possible. Potential applications of these methods in aerosol flocculation and filtration are discussed.
- Research Organization:
- Brookhaven National Lab., Upton, NY (USA)
- DOE Contract Number:
- AC02-76CH00016
- OSTI ID:
- 5066776
- Report Number(s):
- BNL-31561; CONF-820742-1; ON: DE82019527
- Resource Relation:
- Conference: 13. international symposium on rarefied gas dynamics, Novosibirsk, USSR, 5 Jul 1982; Other Information: Portions of document are illegible
- Country of Publication:
- United States
- Language:
- English
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